Effects of sulfur on Mo 2C and Pt/Mo 2C catalysts: Water gas shift reaction

Abstract

Molybdenum carbide (Mo 2C) and Pt/Mo 2C catalysts were evaluated for the water gas shift reaction without and with 5 ppm H 2S. The Mo 2C catalyst was quickly poisoned by sulfur, achieving a rate that was ∼10% of that prior to sulfur exposure. The Pt/Mo 2C catalyst was initially more active than the Mo 2C catalyst and deactivated more gradually to a level similar to that for the Mo 2C catalyst. X-ray photoelectron spectroscopy revealed Mo 2C, MoS 2, and S–Mo on the spent catalysts; the Pt/Mo 2C catalyst also contained PtS. The results are consistent with Mo 2C sites on the Mo 2C and Pt/Mo 2C catalysts being partially sulfur tolerant, in that these sites could be reactivated on treatment in 15% CH 4/H 2 at 590 °C. High activity sites associated with Pt nanoparticles were irreversibly deactivated. Residual activities for the Mo 2C and Pt/Mo 2C catalysts in the presence of H 2S appeared to be associated primarily with the presence of MoS 2 domains.